1. Field of the Invention
The present invention relates to an orthodontic wire ligating member for use in orthodontic treatment. More particularly, the present invention relates to an orthodontic wire ligating member made of a synthetic resin and engaged with a bracket to retain an archwire.
2. Description of the Related Art
Orthodontic treatment methods using brackets, tubes, etc. to correct a row of improperly positioned teeth are well known. In a typical orthodontic method, brackets, for example, are bonded to teeth to shift the positions of the teeth gradually by applying thereto mechanical tension, i.e. pushing force, pulling force, twisting or other elastic restoring force, with an archwire attached to the brackets, thereby correcting the malpositioned teeth. In this treatment method, each bracket has a slot for engagement with an archwire formed in the center of the bracket body. In addition, wings are provided on the outside of the bracket body. After being inserted into the slot, the archwire is held in the slot by using a ligating device that is mounted in engagement with the wings.
As the ligating device, for example, a ligature wire (ligating wire) of stainless steel, an O-ring of polyurethane, or a ligating module is used to ligate the archwire to the bracket. When the ligature wire, O-ring or ligating module is fitted or replaced, a force of not less than 2 to 3 N (Newtons) is applied to the tooth in the form of vibration. This inflicts pain on the patient.
FIG. 18 shows a conventional example in which an O-ring 50 made of an elastic material is used to ligate an archwire 51 to a bracket 52. In this ligation example, the O-ring 50 is mounted by being wound around the wings of the bracket 52 to retain the archwire 51 on the bracket 52 by elastic force.
The ligating method using a ligature wire is a method that has heretofore generally been used. With this method, the ligature wire is gripped by using the tip of a pair of pliers selected according to each particular application, and the wire is wound around the bracket by manipulating the pliers to thereby ligate the archwire to the bracket. These days, however, O-rings made of silicone rubber or a thermoplastic synthetic resin elastomer, e.g. polyurethane, are frequently used as disclosed, for example, in the specifications of U.S. Pat. Nos. 4,038,753 and 4,950,158.
European Publication No. 0 623 320 A1 and the specification of U.S. Pat. No. 5,711,666 disclose techniques relating to self-ligating orthodontic brackets that allow an archwire to be ligated with a simple operation. The former of the two techniques uses a slide member that is slidable to cap the archwire. The latter technique uses a ligating member having a spring effect to ligate the archwire.
In orthodontic treatment, teeth are gradually moved by applying forces thereto in three-dimensional directions using orthodontic appliances such as brackets, wires, etc. To effect efficient tooth movement, it is better to move teeth with an archwire that is retained in such a manner as to be slidable in a friction-free state (i.e. a state where friction can be minimized in the present invention) where unnecessary friction between the archwire and the brackets is minimized when forces required for orthodontics are generated, or in a low-friction state. With the conventional ligating methods using a metal wire, rubber, etc., the archwire is held down to the bracket slot surface with an excessive pressing force. Consequently, static friction, shearing stress by the archwire, etc. occur besides corrective forces required for the tooth movement physiologically. These unnecessary forces make it difficult to effect the desired tooth movement.
Accordingly, as the orthodontic treatment progresses, improper force other than force necessary for the movement of the patient's teeth acts. This gives a foreign body sensation to the patient, irritates the mucous membrane of the mouth, and inflicts orthodontic pain on the patient during the treatment. The technique that uses a self-ligating bracket solves the above-described problems. However, the bracket has a large and complicated structure because it comprises a slide member, a spring member, etc. Further, there are cases where a special-purpose tool is needed to attach and detach the slide member or the spring member to and from the bracket. Accordingly, the orthodontist is required to have proficient skill in ligating.
Moreover, the foregoing conventional ligating methods are unhygienic because food and plaque are likely to be left on the orthodontic appliances. In regard to configuration, the ligating members have a configuration with many projections and recesses. Therefore, the conventional methods have a problem in terms of aesthetics. Accordingly, there is a demand for a ligating technique that inflicts minimal corrective pain on the patient and allows ligating to be effected easily with a simple arrangement.